1. Field of the Invention
The present invention relates to a method of fabricating a dummy wafer, in particular to a dummy wafer that is used in the plasma cleaning and so on.
2. Description of the Related Art
In existing plasma-generating semiconductor fabrication apparatus, when a wafer is processed, reaction products adhere to a processing chamber and floating dust resulting therefrom is generated. In the case of the reaction product adhering to the wafer, a semiconductor element formed on the wafer deteriorates in the characteristics and owing to the floating dust the pattern short defect or the like increases; accordingly, periodical in-line cleaning of the inside of the chamber has to been carried out.
At this time, in order to inhibit a lower electrode base material in the chamber from deteriorating owing to the plasma and to suppress the inside of the chamber from being contaminated, a silicon (Si) dummy wafer is used to be placed in the chamber and to be subjected to the plasma processing. As the dummy wafer for use in the cleaning, since a gas for decomposing the reaction product with the plasma thereof is supplied in the chamber, not a bare silicon wafer but a wafer provided with a silicon oxide film (SiO2) is used.
However, the wafer with silicon oxide film, when exposed to the plasma, is etched and the silicon oxide film is removed from on the silicon wafer. Accordingly, the silicon oxide film is repeatedly formed. In the regeneration of the silicon oxide film, after the wet etching, a silicon oxide film is formed; accordingly, it takes operation steps and fabrication time due to the regeneration.
Furthermore, the number of times of regeneration of the dummy wafer, owing to deterioration of a surface state of the wafer itself and the warping thereof, is increased so that a use lifetime of the silicon wafer is shorten; that is, in total, the number of the wafers that are used results in an increase and the fabrication cost results in an increase. Still furthermore, as other dummy wafer, a ceramic wafer can be considered; however, it is high in the cost. In addition, being different in the surface roughness from that of the silicon wafer when transferring the wafer in the semiconductor fabrication apparatus, or being different in the light reflectance from that of silicon material at the sensing, it is not suitably used in the semiconductor fabrication apparatus in which the silicon wafer is transferred.